Fluorinated Block Copolymers Research Articles

Self-Assembly of Hierarchical High-χ Fluorinated Block Copolymers with an Orthogonal Smectic-within-Lamellae 3 nm Sublattice and Vertical Surface Orientation.

Hierarchical structure-within-structure assemblies offer a route toward increasingly complex and multifunctional materials while pushing the limits of block copolymer self-assembly. We present a detailed study of the self-assembly of a series of fluorinated high-χ block copolymers (BCPs) prepared via postmodification of a single poly(styrene)-block-poly(glycidyl methacrylate) (S-b-G) parent polymer with the fluorinated alkylthiol pendent groups containing 1, 6, or 8 fluorinated carbons (termed trifluoro-ethanethiol (TFET), perfluoro-octylthiol (PFOT), and perfluoro-decylthiol (PFDT), respectively). Bulk X-ray scattering of thermally annealed samples demonstrates hierarchical molecular assembly with phase separation between the two blocks and within the fluorinated block. The degree of ordering within the fluorinated block is highly sensitive to synthetic variation; a lamellar sublattice was formed for S-b-GPFOT and S-b-GPFDT. Thermal analyses of S-b-GPFOT reveal that the fluorinated block exhibits liquid crystal-like ordering. The complex thin-film self-assembly behavior of an S-b-GPFOT polymer was investigated using real-space (atomic force microscopy and scanning electron microscopy) and reciprocal-space (resonant soft X-ray scattering (RSoXS), grazing incidence small- and wide-angle scattering) measurements. After thermal annealing in nitrogen or vacuum, films thicker than 1.5 times the primary lattice spacing exhibit a 90-degree grain boundary, exposing a thin layer of vertical lamellae at the free interface, while exhibiting horizontal lamellae on the preferential (polystyrene brush) substrate. RSoXS measurements reveal the near-perfect orthogonality between the primary and sublattice orientations, demonstrating hierarchical patterning at the nanoscale.

Durable superhydrophobic cotton fabrics based on fluorinated alternating copolymer and silica nanoparticle: Preparation and oil-water separation

The development of superhydrophobic materials has attracted great attention due to their promising potential in a variety of areas including oil–water separation. In this work, durable and robust superhydrophobic cotton fabrics based on fluorinated alternating copolymer and silica nanoparticle are prepared. Silica nanoparticles are in-situ produced and immobilized onto the surface of poly dopamine (PDA) wrapped cotton fabrics, then modified by fluorinated block copolymer (AB2)nA-b-PIPMSAm, followed by removing the iodine on the polymers, to prepare superhydrophobic cotton fabrics with water contact angle up to 160.8°. The prepared cotton fabrics are durable, displaying excellent resistance to varying organic solvents, acids, alkalis, hot water, sonication and mechanical abrasion. High separation efficiency (maximum 99.6 %) and satisfying reusability for continuous separation of oil/water mixtures are achieved. The separation efficiency for trichloromethane/water mixtures is still as high as 94 % even after 50 times of repetitive separation. In addition, water-in-oil emulsion can be also efficiently handled, displaying high practical application potential.

Ionic-Nanophase Hybridization of Nafion by Supramolecular Patching for Enhanced Proton Selectivity in Redox Flow Batteries.

Nafion, as the mostly used proton exchange membrane material in vanadium redox flow batteries (VRFBs), encounters serious vanadium permeation problems due to the large size difference between its anionic nanophase (3-5 nm) and cationic vanadium ions (∼0.6 nm). Bulk hybridization usually suppresses the vanadium permeation at the expense of proton conductivity since conventional additives tend to randomly agglomerate and damage the nanophase continuity from unsuitable sizes and intrinsic incompatibility. Here, we report the ionic-nanophase hybridization strategy of Nafion membranes by using fluorinated block copolymers (FBCs) and polyoxometalates (POMs) as supramolecular patching additives. The cooperative noncovalent interactions among Nafion, interfacial-active FBCs, and POMs can construct a 1 nm-shrunk ionic nanophase with abundant proton transport sites, preserved continuity, and efficient vanadium screeners, which leads to a comprehensive enhancement in proton conductivity, selectivity, and VRFB performance. These results demonstrate the intriguing potential of the supramolecular patching strategy in precisely tuning nanostructured electrolyte membranes for improved performance.

Surface Properties of Films of Linear-Dendritic Fluorinated Block Copolymers Based on N-isopropylacrylamide

Surface Properties of Films of Linear-Dendritic Fluorinated Block Copolymers Based on N-isopropylacrylamide

Fabrication of Durable, Chemically Stable, Self-Healing Superhydrophobic Fabrics Utilizing Gellable Fluorinated Block Copolymer for Multifunctional Applications.

Limited durability and complex materials restrict the application of superhydrophobic fabrics in daily life. In this work, gellable fluorinated block copolymer poly(dodecafluoroheptyl methacrylate)-block-poly(3-(triethoxysilyl)propyl methacrylate) (PDFMA-b-PTEPM) was used to fabricate adhesive-free superhydrophobic poly(ethylene terephthalate) (PET) fabrics via a simple dip-coating technology and sol-gel reaction. The growth of silica nanoparticles builds up a rough hierarchical structure and provides sol-gel reaction sites of PTEPM segments. The grafting of block copolymer significantly reduced the surface free energy of the fabrics, resulting in an excellent superhydrophobicity with a water contact angle of 160.2°. Benefiting from extensive chemical bond grafting and cross-linking of the PTEPM segment, the fabric exhibits excellent durability in mechanical abrasion, chemical treatment, and washing. The coating has withstood 50 sandpaper abrasion cycles and 400 soft friction cycles and can maintain superhydrophobic properties in various solvents, freezing and a wide pH range. These superhydrophobic fabrics with a long life span possess self-cleaning, anti-icing, oil-water separation, and self-healing capabilities. The multifunctional fabrics developed in this study are durable and easy to produce, possessing the potential for applications in industry and daily life.

Functionalized Fe3O4-based methyl methacrylate Pickering PolyHIPE composites costabilized by fluorinated block copolymer for oil/water separation

High internal phase emulsion (HIPE) technology has been emerged as a prodigious source to create tailor-made porous structures. This type of emulsion contains significantly higher amount of water in it, which is only possible with special type of stabilizers. Most specifically, the monomers with sufficiently high solubility in water such as methyl methacrylate (MMA) make it more cumbersome to stabilize in the form of HIPE. Here we have reported the combination of stabilizers including fluorinated block copolymer Poly (2-dimethylamino)ethyl methacrylate-b-Poly(trifluoroethyl methacrylate) (PDMAEMA-b-PTFEMA) and humic acid modified iron-oxide (HA-Fe3O4) nanoparticles (NPs) to stabilize HIPE, which resulted in highly porous and interconnected products. Fluorinated block copolymers with inherent hydrophobic nature along with iron oxide nanoparticles increased the water repellency of MMA based polymeric monoliths. Increasing the amount of stabilizer increased the porosity and BET specific surface area to 83.8% and 27 ± 0.8 μm, respectively. The prepared porous materials demonstrated hydrophobic characteristics while adsorbing oil from the surface of water up to 16 g/g. Moreover, the adsorbed oil from the prepared monolith was recovered by using simple centrifugation method without damaging the structure. This research opens new avenues to prepare more useful oil and water separation materials such as membranes, pollutant adsorbers, and so on.

Elucidating the Impact of Hydrophilic Segments on 19F MRI Sensitivity of Fluorinated Block Copolymers.

A major challenge in the preparation of polymeric 19F magnetic resonance imaging (MRI) contrast agents (CAs) is signal attenuation caused by reduced segmental mobility of partly fluorinated polymers possessing large numbers of fluorine atoms. Previous studies have thus mainly focused on the development of fluorinated segments for improved 19F MRI; however, detailed investigations of the role of hydrophilic segments on imaging performance remain scarce. In this study, three hydrophilic and biocompatible monomers, i.e., 2-(methylsulfinyl)ethyl acrylate (MSEA), oligo(ethylene glycol) methyl ether acrylate (OEGA), and oligo(2-methyl-2-oxazoline) acrylate (OMOXA), were used to prepare perfluoropolyether (PFPE)-containing amphiphilic block polymers through reversible addition-fragmentation chain-transfer (RAFT) polymerization. The effect of the different hydrophilic segments on 19F imaging performance was explored. The three polymers could be readily dissolved in aqueous solutions, forming assemblies with the hydrophobic PFPE as the core and the hydrophilic chains as the shell. Molecular dynamics simulations demonstrate that the POMOXA chains adopt a rigid, extended conformation, leading to a relatively short 19F NMR spin-spin relaxation time (T2), lower NMR detectable 19F spins (i.e., visibility), and the least intense 19F MRI signal. In contrast, although PMSEA-PFPE has a shorter 19F NMR T2 than POEGA-PFPE, the much higher 19F spin visibility enhances its MRI signal intensity. The result confirms the importance of maintaining both high fluorine visibility and long T2 relaxation time to prepare effective CAs and highlight the key role of the nonfluorinated hydrophilic segments in determining these parameters.

Self-healable triboelectric nanogenerators based on ionic poly(hindered urea) network materials cross-linked with fluorinated block copolymers

The versatility of a reactive block copolymer approach to fabricate ionic poly(hindered urea)-based covalent adaptive networks having pendant fluorinated species formulated with ionic liquid for effective self-healable triboelectric nanogenerators.

Visible‐Light‐Enabled Organocatalyzed Controlled Alternating Terpolymerization of Perfluorinated Vinyl Ethers

AbstractPolymerizations of perfluorinated vinyl ethers (PFVEs) provide an important category of fluoropolymers that have received considerable interests in applications. In this work, we report the development of an organocatalyzed controlled radical alternating terpolymerization of PFVEs and vinyl ethers (VEs) under visible‐light irradiation. This method not only enables the synthesis of a broad scope of fluorinated terpolymers of low dispersities and high chain‐end fidelity, facilitating tuning the chemical compositions by rationally choosing the type and/or ratio of comonomers, but also allows temporal control of chain‐growth, as well as the preparation of a variety of novel fluorinated block copolymers. To showcase the versatility of this method, fluorinated alternating terpolymers have been synthesized and customized to simultaneously display a variety of desirable properties for solid polymer electrolyte design, creating new opportunities in high‐performance energy storage devices.

Visible-Light-Enabled Organocatalyzed Controlled Alternating Terpolymerization of Perfluorinated Vinyl Ethers.

Polymerizations of perfluorinated vinyl ethers (PFVEs) provide an important category of fluoropolymers that have received considerable interests in applications. In this work, we report the development of an organocatalyzed controlled radical alternating terpolymerization of PFVEs and vinyl ethers (VEs) under visible-light irradiation. This method not only enables the synthesis of a broad scope of fluorinated terpolymers of low dispersities and high chain-end fidelity, facilitating tuning the chemical compositions by rationally choosing the type and/or ratio of comonomers, but also allows temporal control of chain-growth, as well as the preparation of a variety of novel fluorinated block copolymers. To showcase the versatility of this method, fluorinated alternating terpolymers have been synthesized and customized to simultaneously display a variety of desirable properties for solid polymer electrolyte design, creating new opportunities in high-performance energy storage devices.

Synthesis of Highly Ordered Si-Containing Fluorinated Block Copolymers

Synthesis of Highly Ordered Si-Containing Fluorinated Block Copolymers

Oval cuboid TiO2 particles with mesoporous structure fabricated by using fluorinated block copolymers as templates with photocatalytic performance

In this work, a poly(ethylene glycol)-b-poly(1H,1H,7H-dodecafluoroheptyl methacrylate) (PEG-b-PDFMA) block copolymer was first synthesized by the reversible addition−fragmentation chain transfer (RAFT) polymerization. Then a novel facile approach was developed to fabricate oval cuboid TiO2 particles with mesoporous structure by using the PEG-b-PDFMA block copolymer as a template and titanium tetrabutoxide (TBOT) as a precursor, followed by evaporation-induced self-assembly (EISA) process and calcination process. The results show that the PEG-b-PDFMA block copolymer can control the oriented assembly of nanoparticles and act as templates for the formation of a mesopore. It is found that the mass ratio of TBOT/PEG-b-PDFMA and water content in the solution have a significant influence on the morphology of TiO2 particles. When the mass ratio of TBOT/PEG-b-PDFMA is 0.25/1, oval cuboid TiO2 particles with mesopores are obtained, which exhibits a high photocatalytic activity for the degradation of methylene blue (MB) dye under UV light irradiation.

Study on ultrasliding surface of fluorinated block copolymer for coating

In this study, poly(hexafluorobutyl methacrylate) (PHFBMA) was prepared by atom transfer radical polymerization (ATRP). Then, a diblock copolymer of poly(hydroxyethyl methacrylate)-poly(hexafluorobutyl methacrylate) was synthesized by ATRP using PHFBMA as a macroinitiator and hydroxyethyl methacrylate (HEMA) as a monomer. The structures and composition of the diblock copolymer were verified via infrared spectroscopy, nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC). An amphiphilic diblock copolymer was used to construct a porous membrane using breath figures. The surface morphology of the film was observed by polarized light and field scanning electron microscopy. The hydrophobicity of the porous film was tested using contact angle and dynamic contact angle measuring instruments. With this hydrophobic porous membrane, perfluoropolyether oil was infused for surface modification. The data obtained indicated that the anti-icing and antibacterial properties of the hydrophobic porous membrane improved well after the infusion of the perfluoropolyether oil.

Mixed morphology in low molar mass fluorinated block copolymers

New low molar mass (Mn ~ 20 kg mol−1) polystyrene-b-poly(methyl methacrylate-co-perfluorohexylethyl acrylate) (PS-b-P(MMA-co-FA)) block copolymers were synthesized all consisting of ~70 mol% PS block and ~30 mol% P(MMA-co-FA) block. The amount of FA counits in the latter block was increased (0.5, 1, 3 and 4 mol%) in order to enhance the incompatibility between the two blocks and to form different self-assembled nanostructures. The block copolymers were thermally annealed by Rapid Thermal Processing (RTP) over wide ranges of temperatures and times. Complementary SEM and AFM analyses evidenced that the introduction of FA counits above a critical content (~2 mol%) drove a self-assembly process through mixed morphologies. These were formed at a distance from the polymer–air interface and consisted of perpendicular cylinders of P(MMA-co-FA) in a PS matrix laying at the substrate– polymer interface, and surmounted PS stripes and PS dots. Modification by low amounts of FA produced block copolymer samples that self-assembled in new, mixed nanostructures, even though they possessed much lower molar masses than those of analogous well established PS-b-PMMA block copolymers.

Preparation of golf ball-shaped microspheres with fluorinated polycaprolactone via single-solvent electrospraying for superhydrophobic coatings

1H,1H,2H,2H-Perfluorooctyl polyacrylate (PTFOA) with a controllable molecular weight was successfully synthesized via atom-transfer radical polymerization (ATRP) followed by condensation with polycaprolactone (PCL) to obtain a new fluorinated block copolymer. Then, the copolymer PCL-b-PTFOA was processed via single-solvent electrospraying in chloroform to fabricate hierarchically porous microspheres. The microsphere size could be controlled from 5.13 ± 0.51 μm to 8.61 ± 0.90 μm, and the pore size on the microsphere surface could be controlled from 282.5 ± 42.0 nm to 603.3 ± 99.6 nm. Solvent evaporation-induced phase separation and fluorinated segment migration are the major reasons for the formation of the golf ball-shaped microspheres. In this study, the influence of electro-spraying parameters on the size and morphology of the porous microspheres was systemically studied. The golf ball-shaped microspheres significantly improved the surface roughness and the CA of their coatings reached 167.3 ± 1.7°. Furthermore, a superhydrophobic fabric was produced by pretreating cotton fabric with adhesive followed by coating with PCL-b-PTFOA via electrospraying. The robust superhydrophobicity can be obtained by the stable binding of PCL-b-PTFOA microspheres onto the fibers, with the CA reaching 155.3 ± 1.1°. Electrospraying of the fluoropolymer microsphere coating was proven to be a very promising technique to produce superhydrophobic coatings on textiles through a simple procedure.

Effect of the preparation method on the morphology and proton conductivity of membranes based on sulfonated ABA triblock copolymers

Sulfonated ABA triblock copolymers were synthesized based on ionomers with a hydrophilic block such as sulfonated poly(ether ether sulfone) (sPEES) and hydrophobic blocks such as poly(methyl methacrylate) (PMMA) and poly(pentafluorostyrene) (PPFS). The formation of these copolymers was evidenced by Fourier transform infrared (FTIR), proton nuclear magnetic resonance (1H NMR), and gel permeation chromatography (GPC) analyses. The copolymers were used to prepare membranes by two approaches: direct self-assembly and infiltration of the polymers into anodized aluminum oxide (AAO) templates. The effect of the copolymer chemical structure (fluorinated and non-fluorinated) and preparation method on the properties of the membranes, such as morphology, thermal stability, water uptake, ion exchange capacity (IEC), and proton conductivity, was evaluated. Both methods used to obtain membranes from ABA copolymers synthesized were successful. Morphological characterization showed that the fluorinated membranes prepared by self-assembly exhibited phase separation. This phase-segregated morphology of partially fluorinated block copolymer structures and high density of sulfonic acid groups had a positive impact on proton exchange capacity and proton conductivity. Moreover, methanol permeability was improved in comparison with Nafion® 117. Otherwise, the morphology of AAO membranes pores filled by infiltration was verified, and the proton conductivity was low due to an increase in the tortuosity which affected proton transport. The present study shows that the membranes prepared by self-assembly of sulfonated ABA block copolymers presented the best properties to be applied as proton exchange membranes.

Sulfonated fluorinated block copolymer containing naphthalene unit/sulfonated polyvinylidene-co-hexafluoropropylene/functionalized silicon dioxide ternary composite membrane for low-humidity fuel cell applications

A ternary composite membrane, composed of a sulfonated fluorinated block copolymer containing naphthalene unit (SFBCN), sulfonated polyvinylidene fluoride-co-hexafluoropropylene (SPVdF-HFP), and functionalized silicon dioxide (FSiO2), was fabricated via a simple solution casting method for use as a suitable proton exchange membrane in low-humidity fuel cells. The morphological and structural characterizations verify the successful formation of the ternary composite membrane. TGA and DSC analyses revealed the suitability of the materials for fuel cell applications. The increased water uptake, IEC, and proton conductivity values with increasing hydrophilicity of membranes were obtained by thorough measurements. The fabricated ternary composite membrane containing 10 wt% FSiO2 exhibited a superior proton conductivity (12.3 mS/cm) under dehydrated conditions (90 °C at 40% RH) over the Nafion 117 (7.8 mS/cm) membrane, while at 90 °C at 100% RH, it exhibited a comparable H+ conductivity (93.1 mS/cm) to Nafion 117 (112 mS/cm) membrane.

Julolidine-labelled fluorinated block copolymers for the development of two-layer films with highly sensitive vapochromic response

Fluorinated block copolymers composed of a polystyrene (Sx) first block and a polyacrylate second block carrying hydrophobic/lipophobic perfluorohexyl side chains (AF) were prepared by atom transfer radical polymerization (ATRP). Fluorescence emission properties were imparted to the copolymers by incorporation in the second block of a julolidine-based fluorescent molecular rotor (JCBF). The synthesized block copolymers were used as the fluorescent low-surface energy thin top-layer onto a polystyrene bottom-layer to produce novel two-layer film vapochromic sensors. Contact angle and X-ray photoelectron spectroscopy (XPS) measurements revealed that the two-layer film surfaces were hydrophobic and lipophobic at the same time and highly enriched in fluorine content as a result of the effective segregation of the perfluorinated tails to the polymer-air interface. The fluorescence intensity of the two-layer films decreased significantly when they were exposed to vapours of organic solvents, including tetrahydrofurane, chloroform, and trifluorotoluene. However, an AF content-dependent sensing behaviour was also observed, with the two-layer films containing the copolymer with the shorter fluorinated block giving a more rapid and almost quantitative decrease in fluorescence variation. Fluorescence emission of the films was also proved to vary with temperature. Both the vapochromic and thermochromic responses were reversible after successive solicitation cycles. The fluorescence variation of the two-layer films was much more marked than that of the corresponding PS/JCBF blend, thus providing a system potentially applicable as highly sensitive volatile organic compound (VOC) sensor, thanks to the active role of the fluorinated block in promoting the migration of the fluorophore to the outermost surface layers.

Thermal and photo-RAFT polymerization of 2,2,2-trifluoroethyl α-fluoroacrylate

RAFT polymerization of 2,2,2-trifluoroethyl α-fluoroacrylate (FATRIFE) was studied under thermal conditions and light irradiation in the presence of four chain transfer agents. Polymers with narrow dispersities were obtained in the presence of trithiocarbonate CTA2, and this further led to fluorinated block copolymers.

A study on amphiphilic fluorinated block copolymer in graphite exfoliation using supercritical CO2 for stable graphene dispersion

In this study, poly(2,2,2-trifluoroethyl methacrylate)-block-poly(4-vinylpyridine) (PTFEMA-b-PVP) was synthesized by stepwise reversible addition-fragmentation chain transfer (RAFT) polymerization for the preparation of graphene by the exfoliation of graphite nanoplatelets (GPs) in supercritical CO2 (SCCO2). Two different block copolymers (low and high molecular weights) were prepared with the same block ratio and used at different concentrations in the SCCO2 process. The amount of PTFEMA-b-PVP adsorbed on the GPs and the electrical conductivity of the SCCO2-treated GP samples were evaluated using thermogravimetric analysis (TGA) and four-point probe method, respectively. All GP samples treated with SCCO2 were then dispersed in methanol and the dispersion stability was investigated using online turbidity measurements. The concentration and morphology of few-layer graphene stabilized with PTFEMA-b-PVP in the supernatant solution were investigated by gravimetry, scanning electron microscopy, and Raman spectroscopy. Destabilization study of the graphene dispersions revealed that the longer block copolymer exhibited better affinity for graphene, resulting in a higher yield of stable graphene with minimal defects.